The present invention relates to a method for preparing bone cement.
The invention also relates to a device for preparing bone cement.
When preparing bone cement it is important, considering the future strength of the bone cement, to achieve a bone cement which is as free as possible from pores and the like caused by air or gas inclusions. These inclusions may be caused by remaining air and gases, occurring when mixing the components of the bone cement, which during the mixing procedure are mixed into the bone cement mass.
From SE-9200360-7 it is previously known how to collect dispersed bone cement, by means of the movement occurring under the influence of vacuum in the mixing chamber when the movable wall section is set free, to form a bone cement pillar in the evacuation section of the mixing chamber. To prevent air, to the extent possible, from leaking in one or several O-rings are arranged around the movable wall section. The O-rings will cause an increased friction implying that the movement of the movable section as well as the collection of bone cement thereby will be poor or prevented when the sealing causes too high friction. Consequently it can be stated, for known devices or methods for preparation of bone cement, that it must be accepted to allow some air or gas inclusions.
The object of the present invention is to produce improved removal of air and gas inclusions in the bone cement. In addition assurance is attained that the movable wall section always will be moved and that thereby improved collection of bone cement is obtained.
In one aspect of the invention, a method for preparing bone cement is provided. The constituent components of the bone cement are mixed under vacuum in a closed mixing chamber which is formed with a moveable wall section that is fixed during the mixing process. After mixing is finished, extrusion of bone cement is performed by releasing the moveable wall section and bringing the moveable wall section towards an extrusion opening. As the moveable wall section is brought towards the extrusion opening, the bone cement is compressed.
In another aspect of the invention, a device for preparing bone cement is provided. The device includes a mixing chamber equipped with a vacuum connection, a wall section that is movable in the direction of the opposite part of the mixing chamber, and a device arranged to maintain the moveable wall section in its initial position during the mixing process. An extrusion opening is located opposite to the moveable wall section of the mixing chamber and a sealing device is arranged to openably seal the extrusion opening. Further, an extrusion tool is arranged to apply a force towards the moveable wall section to perform the extrusion. Prior to extrusion, the extrusion opening is sealed by the sealing device for compression of the bone cement.